Mailing-List: contact cygwin-help@cygwin.com; run by ezmlm List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner@cygwin.com Mail-Followup-To: cygwin@cygwin.com Delivered-To: mailing list cygwin@cygwin.com content-class: urn:content-classes:message Subject: RE: pthread_cond_wait does not relock mutex on release MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Date: Thu, 18 Apr 2002 16:57:13 +1000 X-MimeOLE: Produced By Microsoft Exchange V6.0.5762.3 Message-ID: X-MS-Has-Attach: X-MS-TNEF-Correlator: From: "Robert Collins" To: "Michael Labhard" , Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by delorie.com id g3I6vYE16857 > -----Original Message----- > From: Michael Labhard [mailto:ince@pacifier.com] > Sent: Wednesday, April 17, 2002 10:51 PM > To: cygwin@cygwin.com > Subject: Re: pthread_cond_wait does not relock mutex on release > > > Robert and Gerald: > >          Both quite right.  Although adding the SAFE_PRINTF made no > difference in the > output, checking a condition value in a loop made all the > difference.   > Putting a printf in the loop revealed to my surprise that > "spurious wakeups" > were occurring thousands of times per second.  I had naively > assumed that a > condition would stay set until signalled.  Now I'm led to wonder if a > condition variable is any performance improvement over a > simple loop and > short sleep.  Any thoughts? Without knowing what you are trying to achieve, I can't comment. However: in multi-threaded programs, a condition variable will almost invariably be more efficient than a loop + sleep. As for conditions staying set, that isn't the purpose of condition variables: they are designed to allow signalling between threads, to allow efficient use of cpu resources - and to avoid that loop+sleep approach. Rob -- Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple Bug reporting: http://cygwin.com/bugs.html Documentation: http://cygwin.com/docs.html FAQ: http://cygwin.com/faq/